Electrostatics is concerned with the field and potential of stationary electrical charges and electric charge distributions. Problems are this type are almost exclusively concerned with mathematics of geometries using the inverse-square law.

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When to use method of images in Electrostatics?

I am a bit confused about when to use the method of images in E&M? For example, in Griffith's Electrodynamics Example 3.2, the problem reads: A point charge $q$ is situated a distance $a$ from ...
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1answer
429 views

Electric field from conductive to dielectric media

I am interested in the main difference between transitions from electric fields from Conductive to Conductive/ Dielectric to Dielectric and Dielectric/Conductive media. What are the boundary ...
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2answers
30 views

Positive charges “move” from higher to lower potential [on hold]

It's my understanding that whenever an object gains or loses electric charge this actually corresponds to losing/gaining electrons (protons do not move). So how can a positive charge always move from ...
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1answer
71 views

Grounded conducting sphere inside uniform electric field

The problem of a grounded conducting sphere inside a uniform $E$ field in the $z$ direction can be solved by imagining the field be produced by a pair of charges $Q$ and $-Q$ put on the $z$ axis, ...
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1answer
71 views

Physical representation of magnetic vector potential

For time varying potential $$ E= - \nabla(v)- \frac{\partial A}{\partial t} $$ now for scalar potential v we can represent the equipotential surface as a perpendicular surface of the direction of ...
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1answer
1k views

Electric field and insulator or dielectric

I have a uniform electric field $E$ projected from left to right and I placed an insulator or dielectric right in the middle of it. To the left of the insulator, the $E$ is the original $E$. Inside ...
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1answer
65 views

Minimum separation problem

I am trying to solve this problem where two point charges are infinite distance apart(horizontally) but separated by some finite distance vertically. Both are positively charged and projected ...
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0answers
23 views

Electrochemical cell potential - Prigogine book

I'm trying to understand equation 10.2.14 from Prigogine book "Moder thermodynamics": $V=\frac{\tilde{A}}{nF}=\frac{1}{nF}\left(\mu_X^R+\mu_Y^L-\mu_{Xred}^R-\mu_{Yox}^L\right) - \left( \phi^R-\phi^L ...
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1answer
63 views

Does charge of a metal charged by induction determine by which ends of the metal is grounded to?

Does charge of a metal charged by induction determine by which part of the metal is ground to? I draw a diagram to make it simple to understand: Right diagram: When ground is touched with the ...
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3answers
136 views

How to solve the Laplace Equation in the hollow square region?

Suppose the values of $a$, $b$, $V_1$ and $V_2$ is given. I want to find the solution of the Laplace equation, $$\frac{\partial^2 \phi}{\partial x^2}+\frac{\partial^2 \phi}{\partial y^2}=0$$ in the ...
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0answers
24 views

Polarizable molecule in E-field

If we have a linear molecule with a dipole moment $\mu$ in a static electric field $E$, the potential is given by $V = - \langle \mu,E \rangle$. What is the appropriate equation for the potential if ...
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1answer
62 views

What is the correct way to take out equivalent capacitance here?

So here I have a capacitor with two plates , one positively charged and one negatively, as shown in the figure. Now the material between them is $k_1$ for thickness d/2 and $k_2$ for the other d/2. ...
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1answer
79 views

Boundary conditions in Electrostatics

If I have a grounded conducting material, then I know that $\phi=0$ inside this material, no matter what the electric configuration in the surrounding will be. Now I have a conducting material that ...
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1answer
87 views

Laplace's Equation - under what circumstances does it hold?

I'm currently taking an EM course whereby we deal with systems that satisfy Laplace's equation $\nabla^2 \phi = 0$. Examples include permeable sphere in a magnetic field and metal sphere in electric ...
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1answer
49 views

phase difference between incident plane wave incident on a dipole and radiation fields from dipole

i have an incident plane wave and a dipole, consider that plane wave incident on dipole. at this moment what happen for dipole ? we know that after incident of plane wave on dipole, the radiation have ...
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3answers
652 views

how can I find the potential created by spherical capacitor with dielectric material

If we have a spherical capacitor with inner radius or r1 and outer radius of r2, with charges (+/-)q on them and there is a dielectric material (with constant e) in between them with. What kind of a ...
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1answer
130 views

Earnshaw's theorem and springs

Earnshaw's theorem states that the Laplacian of the potential energy of a small charge moving through a landscape full of static negative and/or positive charges (and gravity) is zero. Thus you can't ...
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1answer
163 views

Finding Green function using eigenfunction expansion method

Given the Dirichlet boundary condition, I am to show that the functions that satisfy $(\nabla ^2 + k_{lmn}^2) \psi_{lmn} (x,y,z) = 0$ are given by $\psi_{lmn} = (\frac{\pi}{2x})^{1/2} J_{l+1/2}(x) ...
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1answer
297 views

Dielectric slab counter-intuitive formula?

For the calculation of force on one of the two equal(in magnitude, opposite in sign) point charges separated by $r$ with a dielectric slab of dielectric constant $K$ and width $d$ in between, the ...
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2answers
429 views

How do I express the interaction energy between two charged spheres?

Consider two identical insulating spheres each with radius $R$ and uniform charge $Q$ through their volume. They are separated from their centers by a distance of $d>2R$. Here is my general ...
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4answers
4k views

Electric field outside a capacitor

I know that the electric field outside of a capacitor is 0 and I know it is easy to calculate using Gauss's law. We create cylindrical envelope that holds the same amount of charges (of opposite ...
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6answers
549 views

What is the range of the validity of Coulomb's law?

What is the smallest and biggest distance in which Coulomb's law is valid? Please provide a reference to a scientific journal or book. Just saying that this law is valid from this range to that range ...
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1answer
77 views

can we charge a neutral glass rod by touching it with charged glass rod?

Can we charge a neutral glass rod by touching it with charged glass rod?Can we charge similar objects by contact of which one is charged and other neutral?
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15 views

How does electrostatic force affect electronic devices?

How does electrostatic force generated by two seperate plates having opposite charges affect electronic devices? I know that magnetic fields have some harmful effects to electronic devices but I am ...
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0answers
36 views

Gauss' Law, charge distribution on conductor [closed]

_A point charge $q$ is placed in a cavity in a metal block. If a charge $Q$ is brought outside the metal, will the charge q feel an electric force? Explain how the external charge Q affects charge ...
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249 views

Effect of charges near a parallel plate capacitor

If I charged a parallel plate capacitor. And then, I insert a charged body near one of the plates. Will there be any interactions like attraction or repulsion? What if I disconnected the battery?
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14 views

Is there a simulator for observing the force between two charges comprehensively? [duplicate]

I basically want to observe the electrostatic force between two charges. I want to know if is there a simulator which could both help me to observe and calculate the force between two charges. I ...
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0answers
17 views

Is there a simulator for observing the force between two charges?

I basically want to observe the electrostatic force between two charges. I want to know if is there a simulator which could both help me to observe and calculate the force between two charges. I ...
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2answers
206 views

Calculating the electric potential in cylindrical coordinates from constant E-field

I am having so much trouble with this problem. I feel like I shouldn't be, but I am. A uniform electric field, $\vec{E} = E_0\hat{x}$. What is the potential, expressed using cylindrical ...
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1answer
166 views

Apply Gauss' Law to find Electric Field around nonconducting plastic sheets

The question: Two very large, nonconducting plastic sheets, each 10.0 cm thick, carry uniform charge densities $\sigma_1$,$\sigma_2$,$\sigma_3$ and $\sigma_4$ on their surfaces, as shown in the ...
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4answers
303 views

Divergence of a field and its interpretation

The divergence of an electric field due to a point charge (according to Coulomb's law) is zero. In literature the divergence of a field indicates presence/absence of a sink/source for the field. ...
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1answer
42 views

How is capacitance of a cylindrical capacitor calculated?

I've just begun learning capacitance, and my lecture notes have a section on calculating capacitance for capacitors in vacuum of various shapes, e.g. two parallel plates and concentric spherical ...
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1answer
48 views

Help understanding the solution to a problem regarding kinetic energy of a group of point charges

The problem provided by my professor goes as follows: "Now consider a situation in which all charges are equal to q and they simultaneously become "unglued". What speed will each charge have when a ...
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1answer
39 views

Charging a metallic sphere positive by induction

Bring a negatively charged rod close to a metallic sphere placed on a insulated stand. As the rod is brought close to the sphere, the free electrons in the sphere move away due to repulsion and ...
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24 views

Electrostatics with Yukawa mass

I seem to have forgotten how to solve Laplace's equation when there is a Yukawa mass $\mu$. I want to find the Yukawa potential due to a homogeneously charged sphere of radius $R$ and charge density ...
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3answers
151 views

Maximum potential of a van de graaff generator

I know that we can calculate the maximum potential of a van de graaff generator by ( radius* electric field in which corona discharge begin to form in the surrounding gas( according to wikipedia 30 ...
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1answer
72 views

How we know this solution is unique?

A typical problem where we exploit the uniqueness theorem towards a solution, is finding the potential outside two cylindrical parallel conducting wires (at potentials $V_0$ and $-V_0$) extending to ...
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2answers
30 views

Charging a spherical capacitance

How could one charge a spherical capacitor with a battery or any other emf source?
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0answers
30 views

Effect of humidity on static electricity

I am looking for a reference to a scientific paper or textbook that explains the effect of humidity on static electricity (triboelectric effect). Any help will be highly appreciated.
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14 views

Surface potential resulting from the charge transfer between insulator and conductor

Common non-contact electrostatic voltmeters are used to measure the surface potential. Imagine we place a charged insulator on top of the conducting plate (insulated from the surrounding) and measure ...
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1answer
118 views

An Electric Potential Glued to a Cubic Insulator to Replicate a Point Charge: Charge Distribution

I have been going back over this problem with a friend for the better part of a day: A potential is glued to a cube insulator so that outside of the insulator the field is the same as a point ...
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2answers
29 views

Electrostatics - Inserting a brass plate between two charges

The question is: if I were to insert a brass plate between two charges, what will happen to the force between the charges? Would it increase, decrease or stay the same? Does the brass plate increase ...
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1answer
110 views

How does food plastic wrap get positive and negative charges on opposite sides of the plastic?

Related: Why two objects get charged by rubbing? After reading the above question’s answer given by Luboš Motl in terms of the triboelectric effect, I believe I have a good grasp on how charge is ...
2
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1answer
47 views

Earnshaw Theorem for ionic solids

Is a single molecule of sodium chloride (say) or a cluster of molecules of NaCl unstable, although macroscopically NaCl is in fact, stable? How can I reason this based on Earnshaw's theorem?
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1answer
40 views

Maxwell calculations that predicted the generation of waves (further use for wireless telegraphs)

At this point in this documentary about the history of electricity: https://www.youtube.com/watch?v=oPnS2WO2_0k&t=4m40s the guy says the Maxwell calculations predicted the generation of certain ...
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1answer
37 views

What is the potential field of an ion near the Bohr radius?

I figure that at large enough distances, the potential field of an ion is just the Coulomb potential for its net charge. But what happens at scales comparable to the ion's Bohr radius? Could there be, ...
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1answer
53 views

What gives an elementary particle a charge? [duplicate]

We know that proton is positive, and electron is negative. But where does come notion of negativity and positivity? Does charge come from some specific particles, or they specific order?
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3answers
37 views

Insulators (also called Dielectrics) which cannot conduct Electricity

How Dielectrics as an Insulating materials transmit electric effect without Conducting Electricity ? How its Possible ??
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21 views

Principle of superposition for capacitor

In a capacitor the parallel plates of opposite charge create equal electric fields in opposite directions. We know field outside the capacitor is zero but inside the capacitor it is non zero. My ...
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1answer
158 views

How can one explain the Kelvin Water drop experiment without assuming the container to already possess a positive charge?

Kelvin Water Dropper experiment refers to the electrostatic generator invented by Lord Kelvin, which uses falling water to generate a voltage by electrostatic induction occurring between ...